Subtitles out of sync

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Mikael
Posts: 3
Joined: Fri Apr 30, 2021 9:15 am

Subtitles out of sync

Post by Mikael »

Hi

If I convert a movie with an extern subtitle (srt) and choose to "Burn subtitles into image" the sync is perfect between the movie and the subtitle.

But if I choose to make a VF-version instead the subtitle has a delay on nearly one second. Does anyone know why?

What I can se so is it possible to delay the subtitles in the Timing folder but not to let it starts earlier.

Suggestions?

Best Regards
Mikael
carl
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Re: Subtitles out of sync

Post by carl »

Can you send me your .srt file and the VF DCP that is made? carl@dcpomatic.com
carl
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Re: Subtitles out of sync

Post by carl »

Thanks for sending the files. It's strange, because the timing in the .srt and DCP you sent seem to match. Is each subtitle out of sync by the same amount, or does it vary?
Carsten
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Location: Germany

Re: Subtitles out of sync

Post by Carsten »

Mikael wrote: Fri Apr 30, 2021 1:24 pm
But if I choose to make a VF-version instead the subtitle has a delay on nearly one second. Does anyone know why?

Where does that delay show up? On a cinema projection system?
Mikael
Posts: 3
Joined: Fri Apr 30, 2021 9:15 am

Re: Subtitles out of sync

Post by Mikael »

It is on the cinema screen. I have not check the whole movie but I'll do that soon.
I'd also tried with several new vf-versions with same result.
In the movie there is some parts when they speak thai with english subtitles and there I had the swedish subtitles in perfect sync with the english.
Can the problem be that the blueraymovie is in 25 frames / sec and was converted to 23.976 / sec?
The subtitles keeps the timeline from 25 frames / sec so the differens would be wider the longer the movie runs (as I sad, I haven't check that yet)

Thanks for the help.

Mikael
Carsten
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Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Subtitles out of sync

Post by Carsten »

If it was an issue with the frame rates, it should show up equally for burn-in and timed text? Ist this a SMPTE or IOP DCP/VF?

If you create the DCP as an Interop DCP (even if only for a test), you can directly compare the in/out times from the SRT file with the resulting subtitle XML file. They should be identical. If DCP-o-matic converts the frame rates, they should shift according to the frame rate change, but DCP-o-matic should do this automatically when you add the subtitle file. You could try to adjust video frame rate reference for the subtitles and see if that makes a difference. In 2.14, you will find this under the Timing tab when you select the subtitle file (you need to have full GUI enabled to see it).
In 2.15.x, you need to click on the subtitle file in content list and choose 'Advanced settings'.

This is from an example SRT file:

1
00:00:05,000 --> 00:00:08,000
- lorem ipsum dolor sit amet -


This is from an IOP-DCP subtitle XML file created in 24fps with no special settings:

<Subtitle SpotNumber="1" TimeIn="00:00:05:000" TimeOut="00:00:08:000"

As you see, the timing matches.

This is when I create the DCP as 25fps, and have set the video frame rate reference for the subtitle manually as 23.97:

<Subtitle SpotNumber="1" TimeIn="00:00:04:248" TimeOut="00:00:07:248"

As you can see, because of the faster playback rate, the timing is advanced.

- Carsten
Mikael
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Joined: Fri Apr 30, 2021 9:15 am

Re: Subtitles out of sync

Post by Mikael »

It is an SMTPE DCP/VF
Carsten
Posts: 1746
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Subtitles out of sync

Post by Carsten »

Create a new project and load JUST the subtile MXF file from your SMPTE DCP into it. If you select this file in content list and click on 'View' in the lower left, it will open a list view of your subtitles with the timing. You can compare these timings with the original SRT file.


If you create a VF from an OV, also make sure all DCP settings of the VF are the same as the OV. DCP-o-matic will check most of them, but I don't know if all. Some changes are allowed for VFs.
IoannisSyrogiannis
Posts: 45
Joined: Mon Nov 13, 2017 8:40 pm

Re: Subtitles out of sync

Post by IoannisSyrogiannis »

The data you share, Mikael are a bit confusing:

a) You “convert a movie” (from a BluRay rip?) and choose “Burn subtitles into image”.

b) The “VF-version” you make, is on an OV DCP you made with the same settings and video source as (a), but without using subtitles at all?

c) You write “the blueraymovie is in 25 frames / sec and was converted to 23.976 / sec”. Where did that 23.976 video came from? It surely is not a DCP, because there is no such frame rate on DCPs and as you write, it is not the BluRay video either (even though it could have been).
Was that 23.976 video been used on (a)?
If yes, then the subtitles that were burned into the picture are also 23.976 and you need to sync them anew when you make a VF, because the resulting DCP of a 23.976 fps video would be a 24fps, if no one made any manual changes.
Since Carl writes that the .srt file and DCP package match their timing, frame rate mismatch is the most probable culprit.

So, check the facts:
What is the video file’s frame rate?
Are the external subtitles in sync with the video file? (Play that out with a player on the computer that you make the DCP, like VLC)
Is the DCP without subtitles (the OV) made out of that video file?
What frame rate the DCP (OV) has?

By the way, when you make a subtitles’ VF, you can check synchronisation on the DCP-o-matic. You don’t need to make the VF and ingest.
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